A policy is a written declaration of intent that combines rules and services that define the criteria for resource access and usage. Request for comments (RFC) 2753 defines policy as “the combination of rules and services where rules define the criteria for resource access and usage.” A policy definition includes intent related but not limited to compute, network, security and storage.
Policies are used as a tool for managing complex environments with many resources, such as a software-defined datacenter (SDDC). User's requirements, intentions, and rules are captured in a set of policies. The policies are then used to drive automated processes that enact and enforce the intent of the user. This removes manual human intervention and guarantees the user intent is maintained.
An SDDC enables management of cloud resources such as servers, networks, and storage by enabling programmatic control of those resources. Cloud users want to impose restrictions to ensure the cloud to behave in a desired way. Policies define different restrictions that the cloud must obey. Because automation is central to the operation of the SDDC, policy-based management is critical to the realization of the SDDC.